Electric preheat unit for tubing



R. l. HAHN ET AL ELECTRIC PREHEAT UNIT FOR TUBING Sept. 19, I950 6 Sheets-Sheet 2 Filed May 15, 1948 INVENTORS Sept. 19, 1950 R. I. HAHN EI'AL suzcmc PREHEAT UNIT FOR TUBING 6 Sheets-Sheet 3 Filed May 15, 1948 Q [N V EN TURS BY fir Wm INV N TORS 6 Sheets-Sheet 4 R. l. HAHN EI'AL ELECTRIC PREHEAT UNIT FOR TUBING Sept. 19, 1950 Filed May 15, 1948 Sept. 19; 1950 R. l. HAHN ETAL 2,523,111

ELECTRIC PREHEAT UNIT FOR TUBING Filed May 15, 1948 s Shasta-Sheet 5 IN V EN TORS Sept. 19, 1950 R. l. HAHN EI'AL ELECTRIC PREHEAT UNIT FOR TUBING Filed May 15, 1948 e Sheets- Sheet e Ill EED/l4 V V L,-

INVENTORS Patented Sept. 19, 1950 ELECTRIC PREHEAT UNIT FOR TUBING Rea I. Hahn and Benjamin N. Snyder, Rochester, N. Y., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application May 15, 1948, Serial No. 27,275

6 Claims.

This invention relates to the manufacture of brazed steel tubing which, for example is formed from a single strip of steel into a two-lply tubing by apparatus shown in Nichols et a1. Patent No. 2,195,751. The formed tubing passes through a copper tube brazing bath in a furnace containing a non-oxidizin atmosphere.

The object of the invention is to provide a simple and efiicientunit'for preheating the tubing before it passes into the furnace to a temperature below the temperature of the brazing bath thereby reducing the cost of construction and operation of the furnace by substantially reducing the amount of heat the furnace is required to supply.

Further objects and advantages of the present invention will be apparent from the following description reference being had to the accompanying drawings wherein. a preferred embodiment of the present invention is clearly shown.

In the drawings:

Fig. 1 is a view showing the side of the we heating unit and the brazing furnace in longitu dinal section.

Fig. 2 is a view in the direction of arrow 2 of Fig. 1.

Fig. 3 is a plan view of the preheating unit with an inspection window shown in section.

Fig. 4 is a sectional view on the line 4-4 of Fig. 3.

Fig. 5 is a side view partly in section of the preheating unit and drawn to a larger'scale, the part in section being on line 55 of Fig. 3;

Fig. 6 is a sectional view on line 6-6 of Fig. 3;

Fig. 7 is an end view in the direction of arrow I of Fig. 3;

Fig. 8 is a sectional view on the line 8 --8 of Fig. 5.

Referring to Figs. 1 and 2, the brazing furnace comprises a metal jacket 20, supported by vertical angles 21 resting on the floor indicated by line 22 (Fig. 2) and enclosing thick walls made of layers 23, 24, 25 and 26 of refractory material. The bottom wall layer supports metal I blocks 30 embedded in a layer 3| of refractory cement which support a metal base 32'which supports a brazing tray 33 of the type shown in Nichols et al. Patent 2,197,191. The tubing to be. brazed passes toward the right (Fig. 1) through a tube 34, a flared collar 35, a compressed gas wiper 36, a brazing bath chamber 31, a second compressed gas wiper 38 and an outlet tube 39. This gas is non-oxidizing. The furnace is heated by electrical elements 40. Copper for the brazing bath, is supplied by copper wires which pass down through a tube 41, and are melted by the heat of the furnace. Non-oxidizing gas is introduced into the furnace through a pipe 42. The temperature of the furnace is automatically regulated-through the use of a pyrometer 43. The right end wall of the furnace includes a refractory block 45" having an opening 46 which can be closed by a door 41 having a long notch 48 therein for clearing the tube 39. The door is raised and lowered by the use of the crank 50 connected with a. drum 5! around which passes several turns of cable 52 connected at the lower end with weight 53 and passing around guide pulleys 54 and 55 and connected with the door.

The preheat unit is mounted on a table located adjacent'the left end wall of the furnace. As viewed in Fig-6, the table 60 has parallel angle bars Elsupporting rails comprising plates 62, 63 and 64 connectedwith angles 6| by screws 65 and nuts 66. The rails guide a horizontally movable base 10 to which a rack TI is attached. RJEtCk H meshes with a pinion l2 integral with a shaft 13 journaled in a bearingHa'ttached to an angle BI and operated by handle rods '15 attached to a'hub' 16 which is connected with a shaft. By turning the shaft 13, the location of plate 10' and the preheating unit supported thereon can be adjusted horizontally. The tubing to be preheated passes first between two copper rollers and Bl (Fig. 8) attached respectively to asteel shaft 82 and to a copper shaft 83 journaled respectively in bearing bushings 84 and 85 of carbon or other bearing material having good electrical conductivity. Washers 82a and 83a secured to shafts 82 and 83 respectively by screws 82b and 83b respectively retain these shafts within their bearings. Bearings 84 and 85'are supported respectively by a steel bracket 86 and by a copper bracket 81. Bearing 84 is retained by a ring 84a attached to bracket 86 by screws 84b. Bearings 85 are retained by a ring 85a attached to bracket 81 and by a ring I81 attached by screws I to bracket 81. Screws 88- attach the bracket 81 to plates 89 which support a pin 90 which supports plate 9| attached by screws 92to bracket 86. Thus bracket 86 can be moved into position 85' (Fig. 8) to facilitate threading the tube. Screws 94 (Fig. 5) attach the bracket 81 to a nonconducting plate 95 which screws 96 attach to the base 10.

Base 10 (Figs. 3 and 6) has integral brackets I00 supporting bearing sleeves lll'l on which a tubular shaft 102 is journaled. The shaft 102 pivotally supports arms I03 which are welded to a metal plate I04 which together with plates I05 and H16 form side and top walls of a case section J whose left end wall (Fig. 3) is provided by a plate I? attached by welding to plates I00, I05, I06 and whose right end wall is provided by movable plate I00 secured by screws IIO to plate I05. Screws III and H2 respectively secure blocks IIS and H0 of refractory, non-conducting material which supports a block I I of similar material. Between the left ends (Fig. 3) of blocks IIS and H0 and plate I0! there is a refractory block I0? a which is notched to provide an opening for the tubing and a bar I25 (also Fig. 5). Between the right ends of blocks H3 and I I4 and plate I08 there is a refractory block I08a attached by screws I09 to plate I08. Block I085; notched to provide an opening for the tublllg and to receive a refractory block I081) secured by screws I680 to a plate I3I.

A screw I secures to the shaft I02 a bracket I2I to which screws I22 attach a bus bar i255, said screws and bus bar being insulated by bushings I20 through which the screws pass and by an insulating plate I23. The bar I25 extends over into the chamber in case section J and there it supports a carbon block I26 located between a copper block I2? and a stainless steel block i223 adjacent to a stainless steel plate I28a which, by turning a screw I29 is caused to press against the block I26 to hold it against block I27. Block E26 has a groove I26a for receiving the tubing T. The parts I27 and I28 are secured to the bus bar I25 by screws I30 which also retain a plate l3I insulated from the bus bar I25 by a non-conducting plate I32 and insulated from the screws by non-conducting bushings I33. The case section J rests upon the plate I32 and is free to be moved clockwise about the rod I62 when it is desired to uncover the block I26 when threading the tubing through the heating unit.

To plate I35 (Fig. 4) two metal plates I35 are welded and between these plates is located a non-conducting refractory plate I36 which supports a metal case section K comprising a top plate I37 side plates I38 and strips I38a united by welding. These plates enclose side blocks I35 and a top block I of non-conducting refractory material. The blocks I39 are secured to the walls I38 by screws I381) (Fig. 3). Clips I EI retained by screws I42 secure the block I40 and the plate I36 to parts I37 and I3I respectively. Plate I36 has an opening Hi6 aligned with a pipe tapped opening I41 in plate I3I for making connection with a pipe through which non-oxidizing gas is introduced.

The tubing can be readily threaded through the heating unit since the roller 80 can be elevated above the roller BI, and the case section K can be removed from its supporting plate I36 and the case section J can be moved upwardly from its supporting plate I32 by swinging it about the shaft I02.

Good electrical contact between the tubing and carbon block is obtained by weighted carbon blocks 150 (Fig. 5) which are guided for vertical movement by the block II5. The blocks I are attached to rods I5I which support weights I5Io; and pass through holes in bar I52 which screws I53 attach to a block 554 attached to the upper plate I05. As the blocks I26 and I50 wear due to abrasion by the tubing, the blocks I50 descend to maintain engagement of the tubing with block I26 under constant pressure. As the case section J is moved clockwise (Fig. 6) about the shaft I02 to expose the block I26, for threading the tubing, the weights I5Ia can descend upon the bar I52 which limits downward movement of the blocks I50 relative to the block II5 so that portions of the blocks I50 remain in the notches in block II5. If the case section J is moved about the shaft I02 far enough to cause the weights I5Ia to gravitate away from the bar I52, such movement of the weights is limited by engagement of the weights with the bar I52. After threading the tubing through the groove in the block I26 the case section J is returned to normal position; and, during this return movement, the blocks I50 move downward until they engage the tubing and, thereafter, the plate I52 moves downward relative to the rods I5I.

The structure supported by shaft I02 can be rotated about the aXis of shaft I02 in order to locate the tubing at the desired horizontal level as the groove I26a in block I26 deepens due to wear. This is accomplished by an adjustable strut including a nut i (Fig. 7) which is threaded on a rod 565 attached to a block I66 which a pin I6"! pivotally connects to a block I68 attached to the plate if] by screws I69. The nut I60 has a shank E6I received by notch I62 in a plate I63 welded to plate I3I. The flange I64 of the nut I60 carries part of the weight of the parts pivotally supported by the shaft I02. When it is desired to move these parts clockwise and upwardly the rod I65 is moved counterclockwise about its pivot pin I67 so that the nut I60 is clear of the plate I63.

The side wall I06 (Fig. 3) is provided with an opening therethrough and in alignment with the opening there is a collar I welded to the plate I06 which supports a sight glass I8I retained by ring I82.

The tubing is heated by the passage of electric current from a direct or alternating current source one terminal of which is connected with bus bar I25 by a flexible conductor not shown and Whose other terminal is connected with bus bar I94 (Fig. 8) attached by screw I92 and nut I93 to a bar I9Ia integral with ring I9I which screws I60 attach to bracket 81. The area of contact between the tubing and the block I26 is substantial and consequently the voltage drop between the block and tubing is relatively low. Most of the voltage drop is due to heating the tubing between the block I26 and roller BI. Since the voltage of the tubing where it contacts the rollers 80 and 8| is relatively low there is substantially no arcing between tubing and the rollers. Some of the current can pass from the tubing to the bus bar I94 through roller 80 and its bearing 34 and bearing bracket 86, plate 9|, pin and plates 89.

The tubing is moved through the heating unit and the furnace toward the right in Fig. l by the apparatus which forms the tubing from a steel strip, and also by a tubing wind-up reel (not shown) located adjacent the right end of tube 39 which provides a chamber enclosing a nonoxidizing atmosphere in which the tubing cools between the furnace and the reel.

By turning the shaft I3 counterclockwise by handles I5, the preheating unit can be moved away from the brazing furnace when greater access to the left end of the furnace is required for maintenance purposes.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. Apparatus for heating longitudinally moving tubing comprising a bus bar connectible with a terminal of a current source, a rectangular carbon block fixed to the bar and in direct contact therewith and having a straight groove for receiving the leading portion of the tubing to be heated, said groove providing substantial area of contact with the tubing and remaining the same length as the tubing wears it deeper, means for urging the tubing against the block with constant unit pressure regardless of deepening of the groove in the block as the tubing wears it, a conductor spaced from the block rearwardly with respect to motion of the tubing for engaging a trailing portion of the tubing and means supporting the conductor and providing for electrical connection of the conductor with another terminal of the current source.

2. Apparatus according to claim 1 in which the tubing is urged against the carbon block by Weighted blocks respectively resting upon portions of the tubing extending beyond the carbon block.

3. Apparatus according to claim 1 in which there is a heat insulated case which includes a metal bottom plate supported by and below the bus bar and electric-ally insulated therefrom, a heat insulating member secured upon the upper side of the bottom plate, an upwardly movable section having metallic top and side wall members, and heat insulating top and side members fixed to the inner surfaces of said metallic top and side Wall members, the heat insulating side members being received upon the bottom heat insulating member when said section is in normal position, said section, when moved from normal position, exposing the groove in the block to facilitate threading the tubing.

4. Apparatus according to claim 1 having a base and means for supporting the bar above the base and including provisions for adjusting the bar relative to the base to obtain the required level of the groove in the carbon block as the groove deepens due to wear.

5. Apparatus according to claim 1 having a base, a horizontal shaft pivotally supported by the base and supporting the bus bar, a plate located below and attached to the bus bar and electrically insulated therefrom and providing the bottom of the case, means in addition to the shaft for supporting the bus bar and including said plate and an adjustable strut connecting the plate with the base whereby the required level of the groove in the carbon block can be obtained as the groove deepens due to wear, the case having a movable section normally supported by the plate and enclosing the carbon block and means for pivotally connecting said case section with th shaft.

6. Apparatus according to claim 1 having a base, a horizontal shaft pivotally supported by the base and supporting the bus bar, a plate located below and attached to the bus bar and electrically insulated therefrom and providing the bottom of the case, means for adjusting the bar relative to the base to obtain the required level of the groove in the carbon block as the groove deepens due to wear, the case having a section normally supported by the plate and enclosing the carbon block, means for pivotally connecting said. case section with the shaft, the means for urging the tubing against the carbon block comprising blocks extending through the top of the case section and guided thereby and engageable with portions of the tubing extending beyond the carbon block, rods each attached at one end to a second mentioned block, weights attached to the other ends of the rods, and a plate having holes receiving the rods and supported by the pivoted case section between the blocks and the weights.

REA I. HAHN. BENJAMIN N. SNYDER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,142,306 Clemens June 8, 1915 1,575,994 Laise Mar. 9, 1926 1,629,345 Koref May 17, 1927 2,019,555 Wood et a1. Nov. 5, 1935 2,223,270 Quarnstrom Nov. 26, 1940 

